Such a locking device is described in DE 31 25 632 C1. Longitudinally displaceable selector shafts are allocated to a shift finger. Individual gears of the gearbox can be shifted with the selector shafts. The selector shafts are provided with engagement grooves forming shift planes, in which the shift finger can engage by corresponding axial displacement of a shift shaft. When the engagement grooves lie in a line aligned in the displacement direction of the shift finger, the shift shaft of the gearbox is located in a neutral position in which no gear is engaged. Upon selecting a shift plane, the shift finger engages in one of the engagement grooves of one of the selector shafts. By rotation of the shift shaft with the shift finger, the shift finger pivots and shifts one of the gears. Two radially projecting locking cams are provided on the shift finger. The locking cams are situated in the neutral position, aligned generally horizontally above the engagement grooves and cooperate with fork-like wall portions of the engagement grooves extended as far as the plane of the locking cams. The external periphery of the locking cams is provided with circular symmetry. The fork-like wall portions are matched to the circular arcuate shape of the locking cam and enclose the locking cam with a little play. The locking cams fix the selector shafts in the neutral position. The width of the locking cams is designed so that, taking account of the whole displacement path of the shift finger, each of the selector shafts allocated to the shift finger is fixed. A respective slot is milled in the locking cams. The slots are situated in a common pivoting plane with the shift finger. The width of the slots is slightly larger than the thickness of each individual selector shaft. The slots are situated in a common pivoting plane with the shift finger. After the selection of the shift plane, the shift finger, the slot and the wall portions of a selector shaft lie in a common plane. The selector shaft can be shifted by means of the pivoting shift finger, since the wall portions alternatively dip into the slots of the locking cam in dependence on the displacement direction of the selector shaft. The depth of the slots is designed so that they form end stops for the longitudinal movements of the selector shaft.
The locking device is used in shift devices for shifting gears by means of a shift lever. A respective shift plane is respectively allocated to one or two selectively shiftable gears situated on a gearshaft. Several gears can be shifted by the shift device. A shift plane is allocated to at least one gear, or at most two gears. Each gear can be shifted only in its predetermined shift plane.
The shift lever is arranged pivotably with respect to a housing by means of a support arrangement. The support arrangement makes possible pivoting movements of the shift lever in a selection plane and in a shift plane aligned transversely of the selection plane. The shift lever is guided by a slide during the selection and shifting processes.
The shift lever is located in the selection plane in a neutral position and is pivotable in the selection plane out of the neutral position by the selection of shift planes alternatively into one of at least two inoperative positions. If the shift lever is located in one of the inoperative positions, a shift plane is selected. The shift lever is pivotable out of the inoperative position in the shift plane for shifting one of the gears. The neutral position of the shift lever is for the most part also one of the inoperative positions, from which one of two gears is selectively shiftable.
In the inoperative positions or in the neutral position of the shift lever, selector shafts are located in a middle, neutral position, in which the gears shiftable by means of the selector shafts are not shifted. The shift lever is provided with a shift finger at a free end. Each of the selector shafts has an engagement groove or a shift opening for the engagement of the shift finger. A selective engagement in one of at least two axially parallel selector shafts is performed by selection movements of the shift lever. The shift lever is movably coupled to one of the selector shafts in these positions.
Pivoting of the shift lever in the shift plane out of the inoperative position in one or other direction results in a displacement of the selector shaft coupled to the shift lever, since the shift finger acts on a side bounding the engagement groove. One of the gears allocated to the selector shaft is engaged by the displacement of the selector shaft.
The shift lever is as a rule pivotably received by means of a universal joint in a housing fixed to a vehicle. This joint or this support arrangement provides for a casing of box-like constitution. The casing receives the shift lever and is mounted for pivoting, by means of the shift lever, on the housing fixed to the vehicle, around a tilt axis aligned transversely of the pivot axis. The tilt axis is aligned with the mid-axis of one or two pivot studs, as desired. The pivot studs support the casing in the selection plane pivotably on the housing, however not in the shifting plane. The shift lever is pivotable with the casing (and held fixed in the casing) around the tilt axis in the selection plane. Upon a selection movement at the shift finger, the shift lever pivoting around the tilt axis takes the casing with it. The shift finger is arranged on the shift lever on the side of the tilt axis opposite to the shift force application position (shift knob), and pivots with the shift lever in the selection plane around the tilt axis.
The support arrangement furthermore provides for a support of the shift lever in the casing, pivotably around a pivot axis in the shift plane. The pivot axis runs transversely of the tilt axis. The pivot axis is simultaneously the mid-axis of a pivot stud arranged in the casing. The shift lever is supported on the casing for pivoting around the pivot, however not in the selection plane. The shift finger is arranged at the opposite end of the shift lever to the pivot axis and also supported in the casing pivotably around the pivot axis in the shift plane, however not in the selection plane. The pivot axis and the tilt axis are situated intersecting in a common plane.
With the shift axis and pivot axis of the shift lever situated in one plane, limits are placed on the adjustment of shift forces and shift paths. By shift forces are to be understood the forces which are perceptible at the shift lever by the operator at the point of force application (shift knob) upon selection and shifting. At its point of force application, the shift lever covers defined paths during selection and shifting. Each further point on the lever between the point of force application and the pivot axis or tilt axis also covers paths defined by its distance from the axes. The path, for the most part in radian measure, is dependent on the distance of the shift knob to the axes. At the same pivot angle of the shift lever around the tilt axis or the pivot axis, each of the points covers the same path, independently of whether it is pivoted around the tilt axis or the pivot axis. The shift lever is often guided by a shift slide placed between the point of force application and the axes. The design of slides which save material and space are frequently subject to limitations because of the same path of the shift lever in the slide during selection and shift movements. The shift forces on the shift knob can be affected by the lever ratio of the shift lever. The lever ratio results from the distance from the knob to the axes and from the distance from the axes to the engagement of the shift finger in the engagement groove of the selector shaft. The length of the shift lever projecting into the passenger space is as a rule limited according to construction space. The length of the shift finger, starting from the intersecting axes, is dependent on the position of the elements of the internal shifting arrangements.
The pivoting shift lever is guided during selection of the shift planes and during shifting of the gears by guide paths, e.g., a slide. The pivoting movements of the shift lever in the selection and the shift direction are limited by stops. The stops ensure that the shift finger engages exactly in one of the engagement grooves of one of the selector shafts after the conclusion of selection. The stops limiting the shift path of the shift finger ensure that the selector shaft is displaced exactly into its predetermined position and no further.
Only one gear can be shifted during a shifting process. If two gear are allocated to a shift plane, one of the gears in the shift plane is from the outset not shiftable, or is locked in the shift plane by means of a locking device, while the other is shifted. According to the embodiment of the shift device, the further shift planes adjacent to the selected shift plane are locked against inadvertent or automatic selection. An incorrect selection or shifting is excluded. The gears in the shift planes adjacent to the selected shift plane are locked against inadvertent or automatic selection during the shifting of a gear and when a gear is engaged. The reverse gear is as a rule locked against inadvertent selection or shifting from one of the shift positions or selection positions for respective shifting or selection of the forward gears.